MOLPOP-CEP modelled excitation temperatures of the 3.264 (dark blue), 3.349 (dark orange), and 3.335 GHz (red) ground-state lines of CH, alongside that of the 701 MHz (dashed black) and 724 MHz (dashed-dotted black) lines of the first excited level of CH (where detected) as a function of CH column densities for the physical conditions derived for the 51, 57, 65, 67, and 61 km s⁻¹ cloud components of W51 E (clockwise from the top-left). The inset panels expand on the T_ex values corresponding to CH column densities between 7 × 10¹³ and 3 × 10¹⁴ cm⁻². The region shaded in grey highlights the range of N(CH) values derived toward W51 E for each velocity component.